Japanese Unexamined Patent Publication No. 2001-25187 discloses a conventional example of a stator for use in a rotating electrical machine such as a motor and a generator. This stator comprises a stator core having a circular ring shape, magnetic teeth wound by coils, a midpoint busbar, and collection-distribution busbars. Specifically, the stator core has a laminated or stacked structure consisting of multiple sheets of magnetic steel. The magnetic teeth are arranged around the stator core in the circumferential direction with prescribed distances therebetween and are each projected inwardly in the radial direction, wherein the magnetic teeth are respectively wound by coils via insulating members. The midpoint busbar is a conductive member having a ring-sheet like shape, which connects together all the inner circumferential ends of the coils. The collection-distribution busbars correspond to three conduction members each having a ring-sheet like shape, each of which connects together the outer circumferential ends of every three coils arranged in the circumferential direction.
FIG. 7 shows an example of the exterior appearance of a single collection-distribution busbar. That is, the collection-distribution busbar 30 comprises a ring sheet 30a, an external terminal 30b, and coil terminals 30c. The external terminal 30b projects outwardly in the radial direction from the ring sheet 30a and is connected with an external device such as a power source (not shown). The coil terminals 30c project inwardly in the radial direction from the ring sheet 30a, wherein each coil terminal 30c is connected with an outer end of a coil wound about three magnetic teeth arranged in the circumferential direction. In the collection-distribution busbar 30, the overall area of the ring sheet 30a is coated with insulating paint, which is shown by dashed lines P in FIG. 7. In contrast, the external terminal 30b and coil terminals 30c are not coated with insulating paint, so that they are exposed from the coated surfaces of the ring sheet 30a. 
FIG. 8 shows an example of a stator 37 of a rotating electrical machine, in which the prescribed number of stator cores 31 are arranged in the circumferential direction along with the ring sheet 30a of the collection-distribution busbar 30. Each stator core 31 provides an insulating member 33 having an extended portion 33a, which is extended outwardly in the radial direction. In addition, a coil 32 having two ends 32a and 32b is wound about magnetic teeth 31a via the insulating member 33. Each stator core 31 also provides a terminal member 34 having two connecting portions 34a and 34b. Herein, the first end 32a of the coil is fixed to the extending portion 33a of the insulating member 33 via the first connecting portion 34a of the terminal member 34. The second end 34b of the terminal member 34 fixes the position of the coil terminal 30c, which projects inwardly in the radial direction from the ring sheet 30a of the collection-distribution busbar 30 (see dashed lines in FIG. 8). When the rotating electrical machine is designed as a motor, electric power of a power source (not shown) is transmitted to the collection-distribution busbar 30 via the external terminal 30b. In addition, electric power is distributed to the coils 32 via the terminal members 34, which are fixed onto the extending portions 33a of the insulating members 33.
A midpoint busbar 35 having a ring-sheet like shape is arranged inside of the ring sheet 30a of the collection-distribution busbar 30. The midpoint busbar 35 has the prescribed number of midpoint connection terminals 35a that project outwardly in the radial direction from the midpoint busbar 35 and are sequentially arranged with prescribed pitches therebetween, which are equivalent to pitches of arrangements of the magnetic teeth 31a in the stator cores 31. All the inner ends of the coils 32 are connected together by the midpoint connection terminals 35a. FIG. 9 is an enlarged view of the selected part of FIG. 8 encompassed by a dashed circle. Each insulating member 33 for the magnetic teeth 31 has a second extending portion 33b, which is extended inwardly in the radial direction. A terminal member 36 having two connecting portions 36a and 36b is attached to the second extending portion 33b of the insulating member 33. Herein, the second end 32b of the coil 32 is fixed to the second extending portion 33b of the insulating member 33 via the first connecting portion 36a of the terminal member 36. In addition, the second connecting portion 36b of the terminal member 36 fixes the position of the midpoint connection terminal 35a, which projects outwardly in the radial direction from the outer circumference of the midpoint busbar 35. Thus, the midpoint busbar 35 mutually connects together all the inner ends 32b of the coils 32. That is, the midpoint busbar 35 forms a comprehensive midpoint for all the coils 32.
However, the aforementioned stator 37 has the following problems.    (1) Due to the prescribed positional relationships established between the external terminal 30b and the coil terminals 30c, the three collection-distribution busbars 30 cannot mutually share parts thereof. That is, different sets of parts should be required with respect to different busbars respectively. The three external terminals 30b of the three collection-distribution busbars 30 should be preferably arranged in proximity to each other for the purpose of establishing connections and wiring with the external device. In addition, it is difficult to use common coil terminals among the three collection-distribution busbars 30 because the coil terminals 30c are arranged with prescribed pitches therebetween, which are three times greater than pitches of arrangements of the magnetic teeth 31.    (2) The midpoint busbar 35 differs from the collection-distribution busbar 30 in structure. Therefore, it is impossible to provide the common structure between the midpoint busbar 35 and the collection-distribution busbar 30. This inevitably increases the number of parts, which require a large amount of labor in assembly. In particular, the three collection-distribution busbars 30 resemble each other in shape. Therefore, when they coexist in one place, it is difficult for the worker to discriminate between them. This will reduce the workability in assembly.    (3) The three collection-distribution busbars 30 should be electrically insulated from each other with respect to the coils 32, which are not mutually connected together. The conventional stator 37 is assembled in such a way that the collection-distribution busbars 30 are assembled independently, wherein insulation processes should be reliably performed with respect to all the collection-distribution busbars 30 independently. That is, the conventional stator 37 that requires insulation processes independently on various components requires numerous steps in the manufacture of each single component. In order to ensure insulation performance in a stable manner with respect to each component, it may be necessary to form uniform insulation layers by complicated manufacturing steps such as multilayer coating. This increases the total cost of the product in manufacture.